Synthesis and neurotropic activity of new pyrano[4′,3′:4,5]thieno[2,3:4″,5″]pyrimido[2,3-c]-(1,2,4 )triazines

Full text of DOI:10.1023/A:1010493426085

Pharmaceutical Chemistry Journal
Vol. 35, No. 3, 2001
SEARCH FOR NEW DRUGS
SYNTHESIS AND NEUROTROPIC ACTIVITY OF NEW
PYRANO[4¢,3¢:4,5]THIENO[2,3:4²,5²]PYRIMIDO[2,3-c]-(1,2,4)TRIAZINES
A. Sh. Oganisyan,1 G. O. Grigoryan,1 A. S. Noravyan,1 I. A. Dzhagatspanyan,1
and G. G. Melikyan1
Translated from Khimiko-Farmatsevticheskii Zhurnal, Vol. 35, No. 3, pp. 6 – 8, March, 2001.
Original article submitted May 30, 2000.
Previously we reported that some derivatives of con-
densed thienopyrimidines possess neurotropic properties
[1, 2]. To our knowledge, the synthesis and biological prop-
erties of pyranothienopyrimidino(1,2,4)triazines were not de-
scribed so far. We have developed a method for the synthesis
of new thienopyrimidinotriazines, which are condensed with
a tetrahydropyran ring, and studied their anticonvulsant ac-
tivity.
Finally, the condensation of compounds IVa and IVb with
pyruvic acid in a mixture of acetic acid and ethyl alcohol led
to the formation of tetracyclic compounds (Va, Vb) contain-
ing the pyrimido[2,3-c]-(1,2,4)triazine fragment.
EXPERIMENTAL PHARMACOLOGICAL PART
The anticonvulsant activity of compounds Va and Vb
was studied on rats with model convulsions induced by
corazole (90 mg/kg, s.c.) and characterized by the effective
dose (ED50) preventing the clonic convulsion component in
50% of test animals [3].
In the first stage, we used the reactions of 2-aminothio-
phene (I) [1] with isothiocyanates to obtain thioureido deriv-
atives IIa and IIb. These products exhibit cyclization in the
presence of potassium hydroxide with the formation of the
corresponding 2-thio-4-oxothienopyrimidines (IIIa, IIIb).
Boiled with hydrazine hydrate, compounds IIIa and IIIb
yielded hydrazino derivatives IVa and IVb.
The tranquilizer effect was studied using the “conflict
situation” test. The model conflict between drinking and de-
fense motivations was created in rats with preliminarily de-
veloped drinking reflex. During an attempt at taking water
the animal received electric irritation and, hence, could not
satisfy the dominating need in drinking. The conflict of two
motivations was manifested by anxiety and emotional stress.
The experimental setup provided automated determination of
the amount of water taken (despite the electric irritation), the
number of approaches to the drinking bowl, and the motor
activity. The anxiolytic activity of the synthesized com-
pounds was characterized by an increase in the number of
water takes [4].
COOC2H5
RNCS
COOC2H5
KOH
O
O
S
NH2
S
NH
O
C
S
NH
R
IIa, IIb
I
O
R
S
R
N
N
O
O
O
S
N
N
NHNH2
S
H
IIIa, IIIb
IVa, IVb
The effect of the synthesized compounds upon the mne-
monic functions was studied in rats with a passive avoidance
conditioned reflex (PACR) developed as described in [5] us-
ing electric shock as the amnesic factor. During the test, the
duration of stay in the dark and light compartments of the ex-
perimental setup was measured over a time period of 3 min.
Then the PACR was developed (learned) by a single electric
irritation (via the electrode floor) of an animal visiting the
dark compartment. The memory trace was erased by a single
electroshock applied immediately after learning. A test for
PACR reproduction was performed 24 h after learning. An
R
N
O
N
N
N
S
O
CH3
Va, Vb
II – V: R = CH3 (a), CH2CH2 (b).
1
Mndzhoyan Institute of Fine Organic Chemistry, National Academy of
Sciences of the Republic of Armenia, Yerevan, Armenia.
124
0091-150X/01/3503-0124$25.00 © 2001 Plenum Publishing Corporation

Synthesis and Neurotropic Activity
125
TABLE 1. Neurotropic Activity of Compounds Va and Vb
Antiamnesic effect (time of stay
in light compartment, sec)
Anticorazole activity:
Anxiolytic activity
Compound
ED50, mg/kg
(number of water takes)
1st day
2nd day
Control
–
3.4 (2.3 – 4.5)
12 (6.7 – 17.3)
3.4 (2.3 – 4.5)
3.3 (2.4 – 4.3)
1.6 (1.1 – 2.1)
7.3 (5.1 – 9.1)
1.6 (1.1 – 2.1)
2.7 (2.0 – 3.4)
2.6 (2.3 – 3.0)
2.7 (2.3 – 3.1)
2.6 (2.2 – 3.0)
2.4 (1.9 – 2.9)
4.5 (3.0 – 6.0)
5.5 (4.1 – 6.9)
4.5 (3.0 – 6.0)
33.6 (22.7 – 44.5)
2.4 (2.0 – 2.3)
72.1 (28.7 – 115.4)
2.4 (2.0 – 2.7)
Compound Va
Control
70 (28 – 175)
–
Compound Vb
Control
200
2.6 (1.3 – 3.9)
–
5.0 (2.9 – 7.0)
Phenazepam
Control
0.037 (0.026 – 0.052)
2.3 (0.6 – 4.0)
–
5.0 (2.9 – 7.0)
Pyracetam
n/a
133.2 (86.2 – 180.2)
Notes: Data for anxiolytic effect of compounds Va, Vb, phenazepam, and pyracetam are given for doses 25, 25, 0.5, and
1000 mg/kg, respectively; for antiamnesic affect, 25, 25, 1, and 1450 mg/kg, respectively; values in parentheses indicate
the confidence interval for P = 0.05.
increase in the duration of stay in the light compartment (rel-
ative to control) on the next day was evidence that the drug
possesses antiamnesic properties.
1665 – 1670 cm – 1 (amide C=O bonds) and 3100 – 3400
(NH, NH2).
1
The H NMR spectra were recorded on a Varian T-60
spectrometer using TMS as the internal standard. The mass
spectra were obtained with an MX-1320 spectrometer equip-
ped with a system of direct sample introduction into the ion
source. TLC was performed on Silufol UV-254 plates; the
spots were visualized by exposure to iodine vapor. The data
of elemental analyses agree with the results of calculations
performed using the empirical formulas.
The substances to be tested were introduced by
intraperitoneal injections in the form of suspensions with
Tween-80 in a dose of 10, 25, 50, 100, 200, 1000, or
2000 mg/kg. The injections were made 45 min before the
administration of the convulsant (corazole) or the test for
tranquilizer (anxiolytic) activity, neurotoxicity, and antiam-
nesic activity. Animals in the control group were injected
with pure emulsifier. The reference drugs were phenazepam
and pyracetam [6 – 8].
2-(N¢-Methylthioureido)-3-ethoxycarbonyl-5,5-dimet
hyl-4,5-dihydro-7H-thieno[2,3-c]pyran (IIa). A mixture of
2.55 g (0.01 mole) of compound I and 0.73 g (0.01 mole) of
methyl isocyanate in 50 ml of butanol was boiled for 10 h
and allowed to stand overnight. The precipitated crystals
were separated by filtration and washed with diethyl ether to
obtain 2.14 g (65.4%) of compound IIa; m.p., 194 – 195°C;
Rf, 0.67 (CCl4 – acetone, 2 : 1); C14H20N2O3S2.
1H NMR spectrum in CDCl3 (d, ppm): 12.06 (s, 1H,
NH), 6.90 (s, 1H, NH–CH3), 4.65 (t, 2H, 7-CH2), 4.52 (q,
OCH2CH3), 3.06 (d, NH–CH3), 2.96 (t, 2H, 4-CH2), 2.72 (t,
3H, OCH2CH3), 1.32 (s, 6H, C(CH3)2).
The study of the anticonvulsant activity showed that
compound Va (beginning with a dose of 25 mg/kg) is capa-
ble of preventing corazole convulsions (see Table 1). Com-
pound Vb produced a comparable effect in a dose of
200 mg/kg. In the “conflict situation” test, injections of com-
pound Va (beginning with 10 mg/kg) led to a significant in-
crease in the number of water takes, which is evidence of a
tranquilizer activity. Under the same conditions, phenazepam
was effective in a dose of 0.5 mg/kg, while compound Vb
(25 mg/kg) and pyracetam (1000 mg/kg) were ineffective.
In the model of electroshock amnesia, compound Va
(25 mg/kg) produced a more than 30-fold increase in the
time of PACR reproduction, which was comparable with the
antiamnesic effect of pyracetam in a dose of 1450 mg/kg
(see Table 1). Administered under the same conditions, phe-
nazepam (up to 1 mg/kg) and compound Vb did not signifi-
cantly change the behavior of test animals.
2-(N¢-Benzylthioureido)-3-ethoxycarbonyl-5,5-dimet
hyl-4,5-dihydro-7H-thieno[2,3-c]pyran (IIb). Compound
IIb was obtained by a procedure analogous to that described
above, proceeding from 2.55 g (0.01 mole) of compound I
and 1.5 g (0.01 mole) of benzyl isothiocyanate; yield, 1.7 g
(42.1%); m.p., 148 – 149°C; Rf, 0.72 (chloroform – ben-
zene – acetone, 4 : 4 : 1); C20H24N2O3S2.
1H NMR spectrum in CDCl3 (d, ppm): 11.90 (s, 1H,
NH), 7.17 (s, 5H, C6H5), 6.87 (m, 1H, NH–CH2–C6H5), 4.60
(d, 2H, CH2C6H5), 4.53 (t, 2H, 7-CH2), 4.13 (q, OCH2CH3),
2.70 (t, 3H, OCH2CH3), 1.20 (s, 6H, C(CH3)2).
EXPERIMENTAL CHEMICAL PART
The IR absorption spectra were measured on a UR-20
spectrophotometer (Germany) using samples prepared as
nujol mulls. The IR spectra of the synthesized compounds
exhibit characteristic absorption bands in the regions of
3,6,6-Trimethyl-4-oxo-2-thio-5,6-dihydro-8H-pyrano[
4¢,3¢:4,5]thieno[2,3-d]pyrimidine (IIIa). A mixture of
3.28 g (0.01 mole) of compound IIa and 1.12 g (0.02 mole)
of potassium hydroxide in 50 ml of 50% aqueous ethanol

126
A. Sh. Oganisyan et al.
was boiled for 2 h. Upon cooling, the reaction mixture was
acidified with a 10% aqueous hydrochloric acid solution to
obtain a weak acid reaction. The precipitated crystals were
separated by filtration, washed with water, and dried to ob-
tain 2.70 g (95.8%) of compound IIIa; m.p., 273 – 275°C
(ethanol); Rf, 0.71 (acetone – carbon tetrachloride, 2 : 1);
C12H14N2O2S2.
1H NMR spectrum in C5D5N (d, ppm): 10.2 (s, 1H, NH),
4.70 (t, 2H, 8-CH2), 3.46 (s, 3H, 3-N–CH3), 3.10 (s, 2H,
5-CH2), 1.30 (s, 6H, C(CH3)2).
and 0.88 g (0.01 mole) of pyruvic acid in 50 ml of ethanol
was boiled for 10 h. Upon cooling, the precipitated crystals
were separated by filtration, washed with water, and dried to
obtain 2.0 g (62.3%) of compound Va; m.p., 264 – 266°C
(DMSO);
Rf ,
0.60
(ethanol – chloroform,
1 : 2);
C15H16N4O3S.
1H NMR spectrum in CDCl3 (d, ppm): 4.82 (s, 2H,
10-CH2), 3.48 (s, 3H, 5-N–CH3), 3.02 (t, 2H, 7-CH2), 2.54
(s, 3H, –N=C–CH3), 1.28 (s, 6H, C(CH3)2); mass spectrum,
m/z (Irel, %): M+ 332(53), 303(19), 274(89), 246(100),
177(18).
3-Benzyl-4-oxo-2-thio-5,6-dihydro-8H-pyrano[4¢,3¢:4,
5]thieno[2,3-d]pyrimidine (IIIb). Compound IIIb was ob-
tained by a procedure analogous to that described above, pro-
ceeding from 4.04 g (0.01 mole) of compound IIb; yield,
3.23 g (90.3%); m.p., 252 – 253°C (ethanol); Rf, 0.66 (chlo-
roform – benzene – acetone, 2 : 2 : 1); C18H18N2O2S2.
1H NMR spectrum in C5D5N (d, ppm): 10.76 (s, 1H,
NH), 8.0 – 7.05, (s, 5H, C6H5), 6.0 (s, 2H, CH2C6H5), 4.73 (t,
2H, 8-CH2), 2.98 (s, 2H, 5-CH2), 1.27 (s, 6H, C(CH3)2).
2-Hydrazino-3,6,6-trimethyl-4-oxo-5,6-dihydro-8H-
pyrano[4¢,3¢:4,5]thieno[2,3-d]pyrimidine (IVa). A mixture
of 2.82 g (0.01 mole) of compound IIIa and 5 ml of
hydrazine hydrate in 25 ml of butanol was boiled for 8 h and
allowed to stand overnight. Upon cooling, the precipitated
crystals were separated by filtration, washed with water, and
dried to obtain 2.0 g (72.5%) of compound IVa; m.p.,
252 – 254°C (pyridine); Rf, 0.56 (hexane – ethyl acetate,
1 : 2); C12H16N4O2S.
1H NMR spectrum in C5D5N (d, ppm): 5.70 (s, 1H,
NHNH2), 4.63 (bs, 4H, NH–NH2, 8-CH2), 3.40 (s, N=CH3),
3.15 (t, 2H, 5-CH2), 1.28 (s, 6H, C(CH3)2).
3-Benzyl-2-hydrazino-6,6-dimethyl-4-oxo-5,6-dihydro-
8H-pyrano[4¢,3¢:4,5]thieno[2,3-d]pyrimidine (IVb).
Compound IVb was obtained by a procedure analogous to
that described above, proceeding from 3.58 g (0.01 mole) of
compound IIIb; yield, 2.3 g (64.5%); m.p., 209 – 210°C
(pyridine); Rf , 0.62 (chloroform – benzene – acetone,
2 : 1 : 1); C18H20N4O2S.
5-Benzyl-2,8,8-trimethyl-1,6-dioxo-7,8-dihydro-10H-
pyrano[4¢,3¢:4,5]thieno[2,3:4²,5²]pyrimido[2,3-c]-(1,2,4)-
triazine (Vb). Compound Vb was obtained by a procedure
analogous to that described above, proceeding from 3.42 g
(0.01 mole) of compound IVb; yield, 2.6 g (65.0%); m.p.,
230 – 231°C (DMSO); Rf, 0.58 (chloroform–benzene–ace-
tone, 2 : 1 : 1); C21H20N4O3S.
1H NMR spectrum in CDCl3 (d, ppm): 7.64 (bs, 5H,
C6H5), 5.60 (s, 2H, CH2–C6H5), 4.80 (t, 2H, 10-CH2), 3.00 (t,
2H, 7-CH2), 2.57 (s, 3H, –N=C–CH3), 1.32 (s, 6H, C(CH3)2).
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